For the industrial manufacture of silicone polymer/reinforcing filler compounds, batchwise large-size mixers, for example, kneaders having two sigma blades and planetary mixers are often used in the art. For the continuous manufacture, twin-screw continuous extruder/kneaders are used. Under the current circumstances, it is desired from cost considerations to produce a compound of consistent quality at a high productivity and a low basic unit for energy.
The batchwise mixers mentioned above are able to produce compounds of consistent quality, but take a very long time in powder mixing if the filler has a high bulk density. The overall process time including powder mixing, heating and heat treatment is prolonged. Productivity may be increased using a mixing vessel of a large volume, which requires an accordingly higher power for operation, leaving the problem of increased energy consumption.
JP 4155718 discloses a method for producing a liquid silicone rubber base using two twin-screw continuous kneader/extruder units. This method meets high productivity and other requirements, but suffers from quality consistency because of problems in metering, feeding, and pumping of the filler. When the system is required to accommodate compositions of different type, problems arise because cleaning and switching are difficult, the overall process becomes complex, and more accessories must be attached to increase the initial investment. There is a desire to have a method for preparing a silicone composition at a high productivity while obviating these drawbacks.